Sodium-sulfur batteries are utilized as main constitutive devices of electric power storage and compensation apparatus for load leveling (demand for electric power). Sodium-sulfur batteries are secondary batteries in which molten metallic sodium as a negative electrode active material and molten sulfur as a positive electrode active material are disposed being separated by a β-alumina solid electrolyte having selective permeability to sodium ions. Such sodium-sulfur batteries are constructed as a sodium-sulfur battery system in which a plurality of module batteries comprising a given number of cells connected are further connected and disposed in a frame together with controllers, and the frame is stored in a package. Outer shape of conventional sodium-sulfur battery system is shown in FIG. 8, FIG. 9 and FIG. 10. Inner structures of conventional sodium-sulfur battery system is shown in FIG. 11, FIG. 12 and FIG. 13. In FIG. 12, the arrow indicates flow of air (wind).
In order to efficiently operate (charge and discharge) the sodium-sulfur battery system 10, it is necessary to actuate module battery 4 at a high temperature of 280° C. or higher for the reasons such as temperature characteristics of sodium ion conductivity of the β-alumina solid electrolyte. On the other hand, various members constituting the sodium-sulfur battery system 10 have restriction in heat resistance. Therefore, it is very important to control the actuation temperature of the module battery 4 to a given range (about 280-360° C.). In charging and discharging, the internal resistance charging is endothermic reaction while the discharging is exothermic reaction. Therefore, equilibrium must be maintained between incoming and outgoing of heat in the package 1 so that the temperature of module battery 4 which rises at discharging can lower in charging to the temperature at the starting of discharging.
For the above reasons, in the sodium-sulfur battery system shown in FIG. 8 to FIG. 13, it is important how to suitably control the temperature in the package 1. Hitherto, discharging of heat generated from module battery 4 out of the package 1 has been carried out by natural ventilation which comprises introducing air from a plurality of air inlet louvers 2 provided at one door 5 at one face (front face) of the package 1 corresponding to the position of the module battery 4 as shown in FIG. 12 and discharging the air from air outlet 3 provided at the ceiling of package 1. The size of air inlet louver 2 and air outlet 3 of package 1 and quantity of exhaustion air have been determined after conducting designing of heat ventilation for heat dissipation from module battery 4.
As a prior document relating to package for sodium-sulfur battery, mention may be made of, for example, Patent Document 1.
Patent Document 1: Japanese Patent No. 3474821